Patent GB-955558-A (GB)
Title: Improvements in and relating to grinding machines
IPC: B24B47/06
Filed: 1961-03-23
Abstract: 955,558. Grinding; machine tool details. LANDIS TOOL CO. March 23, 1961 [March 25, 1960], No. 10559/61. Headings B3B and B3D. A grinding machine has a workpiece carrier for feeding workpieces to a grinding position, a grinding wheel rotataby mounted on a grinding wheel support which is movable by a feed mechanism towards or away from said workpiece carrier, said feed mechanism comprising a feed screw and a thread - engaging member in operative relation therewith, continuous moving means operable between predetermined limits for actuating said threadengaging member to move said grinding wheel support, relative to said feed screw, for a preliminary grinding operation, a ratchet mechanism connected to said feed screw independently of said continuous moving means, and means, operable by said continuous moving means at the end of its movement, for causing said ratchet mechanism to resume operation of said feed mechanism by rotating said feed screw by increments, a sizing device, and means actuated thereby, each time a workpiece is ground to size, for reversing said ratchet mechanism from a point to which said ratchet mechanism has advanced. Headstock 11 is supported on machine base 10 and driven by motor 40. Grinding wheel 13 is mounted on a support for movement on base 10 towards and away from workpieces presented by carrier 14. The latter is rotatably mounted on fixed shaft 15 supported on bracket 16 on base 10 and is driven through belt or chain 101 by shaft 103 of index mechanism actuated by index cylinder 35 and including index plunger 38 engaging notches 39. Size gauge member 80 is attached to pistons in cylinders 86 attached to fixed bracket 17 clamped to shaft 15. ' The headstock has a centre 12. Footstock centre 24 is fluid-operated. The workpieces are rotated by a face plate 120 having oppositely positioned driving dogs 121, 122 engageable with the corners 123 of a flange 124 of the workpiece. Face plate 120 rotates first at a slow rate reversely in the event that the corners of the flange prevent endwise movement of the workpiece into proper driving relation with dogs 121, 122. Face plate 120 then rotates forwardly to rotate the workpiece for grinding. The machine is prepared for operation by closing START switch. This energizes solenoid 4 actuating pilot valve 20 of footstock valve 21 whereby footstock centre 24 is retracted. An ejector is simultaneously actuated thus closing limit switch contact 2LS1; the ejector is then reset, opening limit switch contact 2LS1 and closing limit switch contact 2LS2. Retraction of footstock centre 24 closes limit switch 3LS energizing solenoid 2 actuating pilot valve 30 of indexer valve 31 whereby fluid is directed to the head end of indexer cylinder 35 shifting indexer piston 36 to actuate the index mechanism. Operation of the index mechanism includes withdrawing indexer plunger 38 to open limit switch contact 6LS1 and close limit switch contact 6LS2. At the end of the index movement when plunger 38 drops back in notch 39, limit switch contact 6LS1 closes and limit switch contact 6LS2 opens. Footstock centre solenoid 4 is de-energized. After a predetermined intervel, determined by timer relay 11TR, to permit the completion of the index movement, solenoid 3 is energized actuating pilot valve 20 of footstock valve 21 to advance footstock centre 24 into engagement with a workpiece. If the workpiece is short, arm 25 on footstock centre 24 actuates limit switch contact 4LS2 energizing headstock motor relays 5MR, 5ML starting reverse rotation of headstock motor 40 at slow speed. If dogs 121, 122 on face plate 120 are not in proper position relative to workpiece flange 124, they will be backed away from the point of contact on the corners of the flange so that endwise movement of the workpiece against headstock centre 12 may be completed. After an interval, determined by timer relay 2TR, sufficient to allow dogs 121, 122 to back away from any improper contact with workpiece flange 124, relays 5MR, 5ML are de-energized, thus stopping the slow speed reverse movement and transferring the motor circuit to relays 5MF, 5MH to rotate the workpiece forwardly at high speed. If the workpiece is long it will actuate limit switch 7LS as it moves into alignment with footstock centre 24; arm 25 will actuate limit switch 5LS to start the motor 40. The function of limit switch 5LS and limit switch 4LS1 is to co-operate the functions of the footstock centre and the indexer so that one will not interfere with the other. The function of limit switch contact 4LS2 and a corresponding contact (not shown) of limit switch 5LS is to start the motor 40 after the footstock centre has engaged the workpiece. Solenoid 6 is energized, actuating pilot valve 50 of infeed valve 51 whereby pressure fluid is directed to the head end of rapid feed cylinder 52 advancing feed screw 54. Feed screw 54 is engaged by gear 75 at the lower end of shaft 55 supported in wheelbase 83. The operation of footstock centre 24 to engage the workpiece, the starting of motor 40 and the actuation of the wheel feed all occur in response to the closing of limit switch contact 6L1 at the end of the index movement. Feed screw 54 advances until it engages positive stop 69. As wheelbase 83 moves forward, limit switch 12LS is opened. During the rapid feed movement, exhaust pressure from the cylinder 52 holds valve 60 in right-hand position preventing the passage through valve 60 of pressure fluid to the slow feed cylinder 61. When rapid feed stops the exhaust pressure drops and valve 60 shifts to the left to direct pressure fluid to slow feed cylinder 61. Piston 62 actuates rack 63 meshing with pinion 64 on hand wheel shaft 65 to rotate vertical shaft 55 through gear 76 so advancing wheelbase 83. As hand wheel 56 rotates, cam 57 actuates limit switch 11LS energizing solenoid 7 to advance gauge 80 into operative position. Relay 5MH is de-energized and relay 5ML is energized whereby motor 40 rotates slowly forward. When gauge 80 advances, limit switch contact 8LS1 opens and limit switch contact 8LS2 closes, energizing timer relay 4TR. Hand wheel 56 continues to rotate until piston 62 reaches the end of its stroke and at the same time cam 58 actuates limit switch 10LS. Relay 4TR times closed after a predetermined sparkout period energizing solenoid 9 to start increment feed. Solenoid 8 being de-energized valve 70 remains in its right-hand position and retard cylinder 85 is connected through valve 70 to pressure fluid from valve 51 to prevent further movement of wheelbase 83. Solenoid 9 shifts valve 90 to the left directing pressure fluid to cylinder 91 to move piston 92 to the right. Pawl 93 rotates ratchet 95 to turn feed screw 54 for a single feed increment. Timer relay 6TR is energized and closes immediately to energize timer relay 5TR. This times closed de-energizing solenoid 9 and resetting valve 90 for the next stroke. Valve 70 is shifted to connect retard cylinder 85 with exhaust. After a predetermined interval timer relay 4TR times closed. Relay 6TR times open, and is then again energized, valve 70 being actuated to prevent movement of wheelbase 83 beyond the amount. Interaction between the incremental feed and retard mechanism continues until the gauge contact G is closed, de-energizing solenoid 6 causing valve 51 to direct pressure fluid to rapid feed cylinder 52 shifting wheelbase 83 to the right. After predetermined movement piston 53 uncovers port 59 conducting pressure fluid to slow feed cylinder 61 shifting piston 62 downwardly to reset the slow feed mechanism. When wheelbase 83 is retracted it actuates limit switch 12LS when wheel 13 has moved a predetermined distance away from the workpiece. Solenoid 3 and timer relay 2TR are de-energized. When wheelbase 83 reaches retracted position limit switch 9LS is closed. When hand wheel 56 is reset by piston 62, limit switch 11LS is opened, de-energizing solenoid 7 to retract gauge 80, closing limit switch 8LS. Solenoid 4 is energized to retract footstock centre 24. Means is provided whereby the grinding cycle will be stopped and the ports returned to retracted position if the work carrier indexes an empty work station to the grinding position. During slow feed, hand wheel 56 is rotated by piston 62 through a predetermined distance dependent on the length of cylinder 61. During this movement, limit switches 11LS, 10LS are actuated. Closing of limit switch 11LS by cam 57 energizes solenoid 7 to move the gauge 80 into operative position. If there is an unground workpiece in position for grinding it will hold gauge contact G open. However, gauge contact G is not energized until cam 58 actuates limit switch 10LS. When a workpiece is ground to size, solenoid 6 is de-energized, directing pressure fluid to cylinder 52 to retract wheelbase 83. When wheelbase 83 reaches retracted position, limit switch 12LS operates in response to the drop in pressure in the exhaust from cylinder 52 to close a circuit through normally closed relay 7TR to energize relay 8TR. This times closed, energizing solenoid 11 whereby pressure-operated pawl 96 reverses ratchet 95 by a predetermined amount. When the gauge 80 is advanced, the closure of a workpiece will affect the gauge the same as a workpiece that has been ground to size and gauge contact G will remain closed and return wheelbase 83 to starting position.